Preparing your tsunami evacuation plan

By Rebecca Priestley In Science

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20th October, 2012 Leave a Comment

Tsunami - preparing your tsunami evacuation plan

At 9.26am on September 26, I joined the estimated 1.3 million who took part in the New Zealand ShakeOut. I did my Drop, Cover and Hold with a classroom of five-year-olds. Once they were safely under the table, I dived under with them and held onto a table leg until a teacher sounded the all-clear about two minutes later. But if a large earthquake happened when I was at home, my response would not end with Drop, Cover and Hold. Once the shaking was over, I would go outside, open a gate to a neighbour’s garden, then run up the steps of a public walkway to higher ground. I live in a tsunami evacuation zone, coloured yellow on the Wellington Regional Council’s tsunami evacuation maps. This means that in a tsunami with an onshore height of 35m (considered the maximum credible event), my house could be swamped. Nearby, the isthmus between Lyall Bay and Evans Bay is zoned mostly orange – which could be covered by even a 3m wave – as is much of Island Bay, Petone and other low lying parts of Wellington.

In a tsunami generated by a distant earthquake, we could get several hours’ warning. But if you live in a tsunami-evacuation zone, and experience a large earthquake that is “hard to stand up in” or feel a weak earthquake that “lasts for a minute or more”, the Ministry of Civil Defence and Emergency Management advice is to make for higher ground immediately. The ministry’s role is to provide a simple and consistent national message, but getting to high ground – and fast – is not always an option. GNS Science geophysicist William Power says a locally generated tsunami – the most likely scenarios are rupture of faults in Cook Strait or an earthquake at the plate boundary east of the North Island – could arrive at Wellington’s south coast eight to 15 minutes after the quake. Depending on where you live, there might be safer places to be than on the street running for the hills.

In Hawaii, information published by the National Oceanic and Atmospheric Administration’s Pacific Tsunami Warning Centre advises residents the upper floors of “high multi-storey, reinforced-concrete buildings” can provide safe refuge when there is no time to move to higher ground. In some vulnerable parts of Japan, 12m-high steel towers have been built to protect residents from tsunamis. “One of the big learnings out of Japan is that vertical evacuation, in many cases, works well,” says Dan Neely, from the Wellington Region Emergency Management Office (Wremo). “So in areas like Kilbirnie and Lyall Bay, where distance is the biggest deterrent to successful evacuation, we will be working with the community over the next couple of months to identify buildings that might be suitable for vertical evacuation.” Wremo’s Blue Lines Project, a 2010 joint initiative with the local community, marks tsunami evacuation lines on Island Bay streets. The scheme, which last month won a public-awareness award from the International Association for Emergency Managers, is about to be rolled out to other south Wellington suburbs.

Agencies such as Wremo are working at community level to help identify best tsunami evacuation options, although it’s up to households and individuals to identify the best evacuation plan. But Neely tells me to stop worrying about earthquakes and tsunamis. “I’m from Arizona,” he says. “I grew up with flash floods and wildfires, a whole lot of poisonous reptiles and a lot of guns – that was my hazard-scape growing up. You just need to understand what your hazards are and prepare to mitigate those risks. Then go on living your life happily.”

20th October, 2012 Leave a Comment

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